Sheets, such as drawings, blueprints, and graphic arts materials, are often printed or photographed on large pieces of paper, negatives, transparencies or other media and must be stored and transported to prevent damage to the sheets and to allow a viewer to view them. Under many circumstances, sheets must be protected from dust, dirt, light, and moisture, and are most easily used if they are stored flat. Some sheets can be delicate and difficult to replace, and require protection from the force of external impacts.
One method of storing sheets involves rolling the sheets into a cylindrical shape and inserting them into a sleeve, typically made of cardstock or plastic. Blueprints are often stored this way. This can be unsatisfactory because the sheets tend to curl, making it difficult to view them after storage for even short periods of time. Curled sheets often must be laid flat and weighted, both to permit viewing and to smooth the sheets for further use. Many cylindrical containers, particularly when constructed from cardstock, are not sufficiently resilient to protect the contents from damage from impacts, and often do not include light and dust seals, which is important when storing light-sensitive materials.
Another common sheet storage container is a flat, envelope-type container constructed of cardstock. These containers are popular for transporting drawings and other materials, but they too are inadequate. Although the container is flat and stores the sheets in a desirable position, there are no light and dust seals, and paperboard is not sufficiently resilient to withstand impact without damaging the contents. These containers do not adequately protect their contents from moisture. Moreover, cardstock can generate dust which can further harm, scratch, or make dirty the stored product.
Many examples of envelope-type light-tight containers for storing a plurality of sheets of light-sensitive material are known. These containers typically include a lower wall, an upper wall, a hinge connecting the upper and lower walls, and side walls. The hinge permits the container to be opened and closed. For example, U.S. Pat. No. 3,710,977 discloses a container having a latch which is backed with a spring plate and standing walls to prevent light from entering the container. The hinge area is a living hinge that is not light tight. A standing wall and a spring plate must be used to prevent light from entering the container through the hinge.
U.S. Pat. No. 4,431,139 discloses a box that is folded together and requires folding many walls over each other to create a light-tight interior. However, this box is light tight only if the exterior walls are bonded, welded, or taped closed; the box is not light tight absent these extraneous materials. Additionally, this box is not reusable.
U.S. Pat. No. 4,313,538 is directed to a film cassette which has a hinged cover which is added to the cassette as a secondary operation. Walls which prevent light from entering the cassette do not have sufficient clearance with the standing walls in the base of the cassette and interfere with the operation of the hinge.
All of the current containers require that the stored sheets be placed in a light-impervious plastic bag to insure that the sheets are not exposed to light. None of the known boxes, cassettes, or other containers provides a reusable container for light-sensitive sheet material which is light tight without using any external sealing devices or interior bags. None of the known containers can be opened and closed many times while the container provides a light-tight closure each time it is closed. There is a need for a resilient reusable container that is resistant to the entrance of light, dust, and moisture, and that stores sheets flat and is inexpensive to produce.